check_ntp: Nul-terminate jitter data

Make sure the jitter response is nul-terminated before parsing the data
using string functions.

1 files changed, 11 insertions, 1 deletions

diff --git a/plugins/check_ntp.c b/plugins/check_ntp.c
index 0a7640a..a7d278d 100644
--- a/plugins/check_ntp.c
+++ b/plugins/check_ntp.c
@@ -590,6 +590,9 @@ double jitter_request(const char *host, int *status){
                 for (i = 0; i < npeers; i++){
                         /* Only query this server if it is the current sync source */
                         if (PEER_SEL(peers[i].status) >= min_peer_sel){
+                                char jitter_data[MAX_CM_SIZE+1];
+                                size_t jitter_data_count;
+
                                 num_selected++;
                                 setup_control_request(&req, OP_READVAR, 2);
                                 req.assoc = peers[i].assoc;
@@ -623,7 +626,14 @@ double jitter_request(const char *host, int *status){
                                 if(verbose) {
                                         printf("parsing jitter from peer %.2x: ", ntohs(peers[i].assoc));
                                 }
-                                startofvalue = strchr(req.data, '=');
+                                if((jitter_data_count = ntohs(req.count)) >= sizeof(jitter_data)){
+                                        die(STATE_UNKNOWN,
+                                            _("jitter response too large (%lu bytes)\n"),
+                                            (unsigned long)jitter_data_count);
+                                }
+                                memcpy(jitter_data, req.data, jitter_data_count);
+                                jitter_data[jitter_data_count] = '\0';
+                                startofvalue = strchr(jitter_data, '=');
                                 if(startofvalue != NULL) {
                                         startofvalue++;
                                         jitter = strtod(startofvalue, &nptr);